Blast furnace



Aug. 31, 1965 E. G. BAILEY 3,203,585

BLAST FURNACE Original Filed Oct. 10. 1960 2 Sheets-Sheet l E. G. BAILEYBLAST FURNACE Aug. 31, 1965 2 Sheets-Sheet 2 Original Filed Oct. 10.1960 United States Patent ice 5 Claims. c1. 266-30) This inventionrelates to apparatus useful in the reduction of iron ore in accordancewith one of the methods described in my copending patent applicationSerial No. 61,633, filed October 10, 1960, of which this application isa division.

Apparatus of this invention operates upon the principle of converting avertically descending bed of solid organic fuel in such configurationand in such manner as to pro duce clean carbon monoxide ga which emergesfrom a surface of the fuel bed, other than the fuel replenishing surfacethereof, directly into the lower portion of a blast furnace charge ofiron ore and fluxing agents. To this end, the apparatus of thisinvention provides for the support of one side of a descending fuel bedby a gas pervious vertically extending refractory retaining wall. Theopposite side of the fuel bed constitutes the off-ga surface and isdefined, supported, and retained in substantially vertical position injuxtaposition with an adjacent vertically descending ore charge having agenerally horizontally extending top off-gas surface directly beneath astack. For this purpose, the furnace has a generally verticallyextending wall in opposition to the perviou fuel bed retaining wall,between which two walls the juxtaposed organic fuel and ore charge bedsare retained, though the fuel bed retaining wall may be, and preferablyis, of less height than the opposed wall. Separate overhead feedmechanisms are provided, one adjacent the pervious wall for feedingorganic fuel onto the top surface of the descending fuel bed and anotheradjacent the opposed wall for feeding the ore charge onto the top-offgas surface of the descending ore charge. The feed mechanisms,intermittent or continuous, are so controlled that the interface betweenthe fuel bed and ore charge can be substantially parallel to thepervious refractory wall, whereby a fuel bed of substantially constantand predetermined thickness is continuously maintained. The apparatusincludes means for feeding gas, such as air, oxygen, or oxygen-enrichedair, through the pervious wall at suitable temperature and through thedescending bed of fuel directly into the adjacent descending ore charge,and the volume of the gas and the thickness of the fuel bed arecontrolled to cause only incomplete oxidation of carbon in the solidfuel to carbon monoxide.

Because the off-gas surface of the fuel bed is covered by the juxtaposeddescending ore charge, such off-gas interface as well as the interior ofthe bed, along most of its height, may be maintained at a temperatureexceeding the liquid flowing point of the non-combustibles contained inthe solid fuel and hence these non-combustibles, which at suchtemperatures are either themselves molten or part of a flowableeutectic, tend to drain downwardly through the fuel bed in liquid formand are thus gravity separated from the gaseous stream flowingtransversely through the descending bed. This descending fiow also actsin the manner of a gas washer to minimize unburned fuel particlesproceeding with the gaseous reaction products produced in the fuel bedinto the ore charge.

In some cases, supplemental heat input may be provided to the ore chargefrom electrodes or from other strategically disposed subsidiary orsupplemental solid fuel feeds. In other cases, steam may be introducedwith the combustion-supporting gas to limit the upper temperaturedeveloped in the fuel bed.

3,203,685 Patented Aug. 31, 1965 Great advantages accrue from using asthe sustaining vertically descending charge ore which is not intermixedwith solid carbon fuel such as the coke used in the present blastfurnace operation; for the fuel bed operation is controlled to insurethat sufiicient carbon monoxide gas emerges from the fuel bed to reducethe ore contained in the retaining bed without the necessary generationof further carbon monoxide gas within the ore charge from non-oresources. The entire solid fuel requirement for performing the iron orereduction originates within the fuel bed outside of the ore charge.

Absence of fuel carbon in the reducing Zone of the ore avoids the lesspredictable complicated endothermic reactions which take place in normalblast furnace operation. It tends to avoid loss of reducing gas which isnot put to effective reactive use before escape. It makes possibleoperation with a much more nearly complete combustion within the orecharge of the carbon monoxide to carbon dioxide with the oxygen obtainedfrom the reduction of 2Fe 0 to 4Fe+30 before the gaseous flow reachesthe ofi-gas surface of the ore charge.

in some cases provision is made to feed some fuel with the ore in orderto supply sufficient additional heat to maintain the heat balance or tosupply further carbon for generation of carbon monoxide in the reducingzones, depending upon whether the values in the clean heat-laden carbonmonoxide off-gases can be recovered in useful further reactions or heattransfer.

These and other objects of the invention will be more readily understoodwhen taken in connection with the description of the accompanyingdrawings wherein:

FIG. 1 is a vertical cross section through an iron reduction furnacedesigned for operation in accordance with this invention, being brokenaway to indicate extent;

FIG. 2 is a plan view, partly in cross section, also broken away toindicate extent, of the furnace taken along line 2-2 of FIG. 1; and

FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG. 1.

FIG. 1 shows a furnace comprising a refractory hearth 18. An upstandingrefractory wall 19 merges into an inclined imperforate refractorysupporting surface 20. The back of the apparatus includes a furtherupstanding refractory wall 40 communicating with a plenum chamber 42which is connected to a source of combustion-supporting gas such aspreheated air, oxygen-enriched air, or oxygen, supplemented if desiredby a steam inlet or a gas fuel inlet. A series of adjustable baffles 44aid in directing the combustion-supporting gases into uniform, orotherwise distributed, flow along the height of the well through spacedapertures 45, provided by spacing refractory bricks.

Arnanged over the furnace chamber are two feeds and 51, one for fuel andone for the ore charge, each pro vided with a conventional screw feedmechanism for distributing the material in a continuous manner acrossthe width of the furnace. The first feed 50 is located over the rearportion of the furnace and the second feed 51 is at the top of a casing63 having downwardly diverging walls 6t; and 68.

Above the feed 51 is a stack 52 for the off-gases.

A supplemental combustion-supporting gas inlet 53 is positioned abovethe fuel feed 50 and an adjustable pivoted gate 55 is provided justbelow the fuel feed 50 in order to control the thickness of the fuelbed. The gate 55 will have to be water-cooled (not shown), and it shouldbe understood that water-cooled screen tubes or other Water-cooledstructure may be utilized in partial or entire replacement of therefractory walls, as needed.

The apparatus may also contain electrodes 64 along the upper portion ofthe walls 66 and 63 and supplemental air inlets 61 for introduction ofair or gaseous fuel if required.

In operation, any free-burning solid fuel may be fed at the feed 50while essentially ore and proper proportions of limestone and dolomite,or the calcined products thereof, may be fed at the other feed -1. Byproperly controlling the two feeds, an interface is maintained by thejuxtaposition of the beds of different content, thus maintaining anorganic fuel bed of substantially uniform thickness and comprising aZone I of sufficient thickness to prevent complete combustion of thecarbon with the result that the gases emerging rat the interface intoZone '11 are substantially entirely carbon monoxide or CO-f-H in casesteam is used for limiting the temperature of the fuel bed.

The result is that hot gases, i.e., above 1500 F, and preferably above2700 2732 E, proceed across the interface into reduction Zone II in suchvolume IRS to reduce the ore with conversion of the carbon monoxide intocarbon dioxide.

The reduction zone is very simple with only the ore, stone, and slagfiowing downwardly from Zone HI, where the charge is fully preheated bythe rising areas which, by heat exchange to the incoming ore charge,:are cooled to less than 300 'F., and in Zone II the counterflow of hotgas, rich in carbon monoxide and possibly H completes the reduction ofthe FeO toFe. The gas continues its upward flow as in the standard blastfurnace Where the remaining carbon monoxide and H reduce the Fe O and FeO to FeO, and these reactions cease only when the reducing gases attaintheir equilibrium pressure. Ali of the oxygen comes from the ore, andits combination with CO and H supplies the greater part of the heat thatis necessary to support the reducing reactions.

There need be much less CO or H escape unburned as is inevitable withthe standard blast furnace where the fuel is fed in with the ore chargeat the top of the furnace, and much is Wasted from the loss of CO and Hproduced in a zone where they cannot possibly be used before escape.

The rate at which the ore charge is supplied in the present process isproportioned to the supply of reducing gases, CO :and H as indicated bygas temperatures and gas analyses at the proper points.

When using solid fuel with air as the oxidant, either the :fuel or theair, or both, may be preheated. Air at 280 P. will burn some carbon toCO to provide the required temperature in Zone I. The air can bepreheated to 1300 or higher, as cost permits.

The ore charge must be adequately heated and calcined before enteringthe final stage of the reducing zone, as there is a close balancebetween the heat required for reduction and that made available from thecombustion of CO and H using the oxygen released from the ore charge bythe reduction.

If the sensible heat in the gas leaving the reduction zone is notsufiicient to fully heat the ore charge, the extra 'heat may be suppliedelectrically through electrodes 64 or by using a surplus of fuel in ZoneI, in proportion to the ore being reduced, and burning this excesscarbon monoxide with air injected at the proper place, as at of in ZoneHI. Alternately, this heat may be supplied by adding another fuel, forexample CH together with the required air at 61. Some solid fuel may beadded with the ore charge and burned with :air supplied at 61. Whenthere is a surplus of heat as sensible heat of the off-gases, it may beused for preheating air, fuel or for other economic purposes.

Molten slag and molten iron collect at the bottom of the furnace and maybe tapped at 24 and 26, respectively.

High ratios of CO/CO-I-CO by volume and temperatures above 2200 P. canbe readily maintained near the bottom of the ore charge, as is necessaryto accomplish the FeO to Fe reduction. For example, the CO/CO-l CO;ratio by volume should be about 75% at 2200 F. and

l at 2700 =F., or of the order of 72% on a weight or pound-moi basis.

However, the reduction of Fe O rand Fe O to FeO takes place at muchlower carbon monoxide contents (as little as 20% carbon monoxide in thepresence of 10% E 0 and at temperatures as low as 1200 F). Thus in theupper part of the furnace, the lower carbon monoxide, lower temperaturereduction can take place.

Some natural gas containing CH as a principal constituent may also beintroduced as part of the gas flowing through the perforate rear wall40.

For :an example of operation in the furnace of this inention, referenceis made to the figures, including heat balances, given in my copendingapplication, Serial No. 61,633 filed October 10, 1960, but which are notrequired for an understanding of the apparatus aspect of the inventionherein claimed.

Arrows utilized in the drawings relate only to the flow direct-ion ofgases, as distinguished from fuels and liquids. Fuels used may beanthracite, coke, charcoal, dry wood, or any free-burning fuel.

Although a specific embodiment of apparatus of the invention has beendescribed herein, it is not intended to limit the invention solelythereto, but to include all of the obvious variations and modificationswithin the spirit and scope of the appended claims.

What is claimed is:

1. A blast furnace having walls forming a closed chamber, including apair of opposed generally vertically extending walls merging at theirtops into a furnace stack, one of said Walls having a lower gas pervioussection and an upper solid section extending upwardly in laterallyofl-set relation with respect to said lower section, first overhead feedmeans between said lower section and said upper section for feedingsolid fuel into said chamber to form a burning descending solid fuel bedsupported on its rear side by said pervious wall section, secondoverhead feed means disposed adjacent said other wall underneath saidstack for feeding material, including ore, into said chamber in adescending bed having one side of its upper portion supported by saidupper solid wall section and having its bottom portion on said side injuxtaposed relation to and supporting and retaining at least a portionof the front side of said burning fuel bed, and means for conducting ablast of oxygen-containing gas through said pervious wall into the rearside of said fuel bed to drive hot gaseous reaction products of saidfuel into said retaining bed for reaction with said ore and forascending passage through the upper portion of said ore bed and throughsaid second feed means into said stack.

2. Apparatus as claimed in claim 1 having means at the bottom of saidfurnace for collecting materials liquefied in both of said beds duringoperation of said furnace.

3. Apparatus as claimed in claim 1 having air inlets extending throughthe vertically extending Walls of said closed chamber at a level abovesaid first overhead feed means for directing oxygen-containing gassupplied to said air inlets directly into the sides of said retainingbed without passing through said fuel bed.

4. Apparatus as claimed in claim 1 having gate means for maintaining thecontacting interface between the materials fed from said separate feedmeans in a generally vertical substantially constant fixed planesubstantially parallel to said lower pervious wall section and means formoving said gate means into a plurality of different horizontally spacedpositions to vary the thickness of said fuel bed by varying thehorizontal distance of said interface from said lower pervious wallsection.

5. Apparatus as claimed in claim 1 having means for conducting gas downinto the top of said fuel bed to aid in driving all said gaseousreaction products of said fuel into said retaining bed.

(References on following page) 6 References Cited by the Examiner2,345,067 3/44 Osann 26620 X 2,846,301 8/58 Greenwalt 75-40 UNITEDSTATES PATENTS 2,846,302 8/58 Greenwalt 75 40 10/ 08 Meissner 26625 3/20Mace 266-25 5 OTHER REFERENCES 9/24 Kirby 7541 Iron and Steel, 3rdedition, pages 1161-162. Edited by 9/32 Bunce X Tieman, published in1933 by McGraw-Hill Book Co., 1/33 y- New York. 12/34 Klencke 75-89 1/39Ahlmann 10 JOHN F. CAMPBELL, Przmary Exammer. 1/43 Greenwalt 7 5-40DAVID L. RECK, MORRIS O. WOLK, Examiners.

1. A BLAST FURNACE HAVING WALLS FORMING A CLOSED CHAMBER, INCLUDING APAIR OF OPPOSED GENERALLY VERTICALLY EX-I TENDING WALLS MERGING AT THEIRTOPS INTO A FURNACE STACK, ONE OF SAID WALLS HAVING A LOWER GAS PERVIOUSSECTION AND AN UPPER SOLID SECTION EXTENDING UPWARDLY IN LATERALLYOFF-SET RELATION WITH RESPECT TO SAID LOWER SECTION, FIRST OVERHEAD FEEDMEANS BETWEEN SAID LOWER SECTION AND SAID UPPER SECTION FOR FEEDINGSOLID FUEL INTO SAID CHAMBER TO FORM A BURNING DESCENDING SOLID FUEL BEDSUPPORTED ON ITS REAR SIDE BY SAID PERVIOUS WALL SECTION, SECONDOVERHEAD FEED MEANS FISPOSED ADJACENT SAID OTHER WALL UNDERNEATH SAIDSTACK FOR FEEDING MATERIAL, INCLUDING ORE, INTO SAID CHAMBER IN ADESCENDING BED HAVING ONE SIDE OF ITS UPPER PORTION SUPPORTED BY SAIDUPPER SOLID WALL SECTION AND HAVING ITS BOTTOM PORTION ON SAID SIDE INJAXTAPOSED RELATION TO AND SUPPORTING AND RETAINING AT LEAST A PORTIONOF THE FRONT SIDE OF SAID BURNING FUEL BED, AND MEANS FOR CONDUCTING ABLAST OF OXYGEN-CONTAINING GAS THROUGH SAID PERVIOUS WALL INTO THE REARSIDE OF SAID FUEL BED TO DRIVE HOT GASEOUS REACTION PRODUCTS OF SAIDFUEL INTO SAID DETAINING BED FOR REACTION WITH SAID ORE AND FORASCENDING PASSAGE THROUGH THE UPPER PORTION OF SAID ORE BED AND THROUGHSAID SECOND FEED MEANS INTO SAID STACK.